%hash = (
   # the sub { ... } means that this is a closure (a subroutine reference)
   command1 => sub { "command_name -n $var1 -p $var2" }
);

$var1 = 'foo';
$var2 = 'bar';
# added "->()" because we are dereferencing a subroutine reference... a closure
system ($hash{'command1'}->());